Classification of the genus Acacia (in the wider sense) has been subject to considerable debate. It is generally agreed that there are valid reasons for breaking it up into several distinct genera, but there has been disagreement over the way this should be done. As of 2017, it is widely (but not completely) accepted that the section that includes the majority of the Australian species should retain the name Acacia, whilst other sections of the genus should be transferred to other genera. This species is transferred to Vachellia[].

Common Name: Sweet Acacia

General Information

Vachellia farnesiana is a small, spiny, much-branched, deciduous shrub or tree with a wide, low crown; it can grow 2 - 7 metres tall. The short, crooked bole can be 15 - 35cm in diameter[, ]. The plant can form dense, spiny thickets[].
A multipurpose tree with a wide range of uses as a food, medicine and source of materials. It is often cultivated, especially in and around Cannes, southern France, for the essential oil in its flowers which is much used in perfumery[, ]. The tree has potential for use as a protein-rich food and nutritional supplement. It is also cultivated for its flowering branches, which are sold as cut flowers, and is often grown as an ornamental, valued especially for its sweetly fragrant flowers that can be produced all year round[].
Acacia farnesiana is an aggressive colonizer and is regarded as an invasive weed both in parts of its native range and where introduced, notably in Australia, the USA, and some Pacific and Caribbean islands[]. In Australia it is a potential weed of grasslands, invading trampled areas, particularly along watercourses[]. The plant has often escaped from cultivation and has been classified as 'Invasive' in many areas[].

Known Hazards

The seeds, containing an unnamed alkaloid, are used to kill rabid dogs in Brazil[].
Especially in times of drought, many Acacia species can concentrate high levels of the toxin Hydrogen cyanide in their foliage, making them dangerous for herbivores to eat.

Botanical References

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Range

Naturalized through the tropics - the original range is uncertain, but is probably the northern part of tropical America, possibly to southern USA.

Habitat

Dry sandy soils in pinelands, hammocks and disturbed areas in south-eastern N. America[]. It sometimes forms impenetrable thickets, although in most areas it forms a more open cover[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Deciduous Shrub
Height	9.00 m
Growth Rate	Fast
Pollinators	Bees
Cultivation Status	Cultivated, Ornamental, Wild

Cultivation Details

Originally tropical, Vachellia farnesiana can succeed from the warm temperate to tropical areas, where it is naturalized at elevations up to 400 metres and cultivated up to 1,200 metres[, ]. It is particularly well adapted to arid and semi-arid grasslands and wastelands[]. It grows best in areas where annual daytime temperatures are within the range 20 - 32°c, but can tolerate 7 - 42°c[]. It prefers a mean annual rainfall in the range 400 - 1,400mm, but tolerates 150 - 4,000mm[]. It prefers a minimum temperature no lower than 7°c[]. Whilst this species is not very tolerant of cold, being damaged by even a few degrees of frost, the variety Acacia farnesiana cavenia seems to be more resistant to both drought and frost; and is said to be able to withstand short periods with temperatures falling to around -5°c[].
Prefers a light sandy loam and a very sunny position sheltered from strong winds[, , ]. Plants can grow well in pure sand[]. Most species in this genus become chlorotic on limey soils, though this species is said to have some tolerance[]. Established plants are very drought tolerant[, , ]. The species and its cultivars are highly adaptable, and are reported to exhibit tolerance to drought, high pH, low pH, salty soils, both sands and clays[, ]. Plants tolerate a pH range from 5.0 to 8.0[].
Acacia farnesiana is an aggressive colonizer and is regarded as an invasive weed both in parts of its native range and where introduced, notably in Australia, the USA, and some Pacific and Caribbean islands[]. In Australia it is a potential weed of grasslands, invading trampled areas, particularly along watercourses[]. The plant has often escaped from cultivation and has been classified as 'Invasive' in many areas[].
A fast-growing plant[]. In a suitable climate, the trees begin to flower from their third year[].
The flowers are sweetly fragrant. Young trees produce up to 1 kilo of flowers a year[]. A well-managed mature plant 10 years old can yield 9 kg of flowers each year[].
Although damaged by fire, the plant usually resprouts quickly from the base[].
The plant responds well to coppicing[].
The leaves are peculiarly sensitive to changes of weather. When a cloud obscures the sun the opposite leaflets close together and so remain until the sky brightens. They also close at night, the plant appearing to sleep until the sun rises[].
This species has a symbiotic relationship with certain soil bacteria, these bacteria form nodules on the roots and fix atmospheric nitrogen. Some of this nitrogen is utilized by the growing plant but some can also be used by other plants growing nearby[].

Edible Uses

An essential oil from the flowers is used as a food flavouring[]. Cassie absolute, produced from cassie concrete, is occasionally used in flavours. In very low concentration it imparts a delightful naturalness and body to raspberry flavours[].

A low-quality gum obtained from the plant is used to prepare sweets[].

Seed pods - roasted and eaten by Australian Aborigines[, , ].

The seeds are rich in protein (they contain around 23% protein, 53% carbohydrate and 12% fat) and have potential for use as a human food[]. The dried, powdered seed has a digestibility rating of 73%, increasing to 82% when cooked - this is higher than for many of the commonly eaten legume foods. The seeds do contain antinutritional factors, including trypsin inhibitors, phenols, alkaloids and haemagglutinin, but these are not present in high enough concentration to constitute a major nutritional problem. These antinutritional factors are soluble in saline solutions and can be removed by soaking or during cooking[].
The sprouted seeds are said to be edible[]. A popular vegetable[].

The leaves have an acid flavour. They can be used as a substitute for tamarind (Tamarindus indica) in chutneys[].

Medicinal

The bark is astringent and demulcent[]. It is used in the treatment of coughs[].
A decoction of the bark is used as a bath in the treatment of typhoid[]. The juice of the bark is applied topically to treat swellings, bleeding gums etc[, ].

The gummy roots have been chewed as a treatment for sore throat[, ]. A decoction of the root is used as a remedy for tuberculosis[].
A decoction of the gum from the trunk has been used in the treatment of diarrhoea[].

The flowers have been used as an antispasmodic, emetic, stimulant and stomachic[, ]. They are taken by women in Java after giving birth[]. An infusion is used in the treatment of dyspepsia and neuroses[]. A decoction is used to treat a prolapsed rectum, and is taken as an injection in the treatment of leucorrhoea[].
The flowers are added to an ointment, which is rubbed on the forehead to treat headaches[, ].

The tender leaves are bruised with a little water and then swallowed as a treatment against gonorrhoea and affections of the bladder[].
The powdered dried leaves have been applied externally as a treatment for wounds[]. A decoction of the leaves is used as a wash to treat ulcers and sores, after which the young leaves are then applied as a poultice[].

The green seedpods are very astringent. A decoction has been used in the treatment of dysentery and inflammations of the skin and mucous membranes[, ]. An infusion of the pod has been used in the treatment of sore throats, diarrhoea, leucorrhoea, conjunctivitis, and uterorrhagia[].

The pulp of the pods is used in France as a purgative[].

Agroforestry Uses:

In suitable climates, especially in India, Irag and the Mediterranean, the plant is grown extensively as a hedge and windbreak[, ]. The trees have also been used for erosion control in sandy soils[, ].
A good bee plant - the flowers are highly attractive to bees[, , ].

Other Uses

A high-quality essential oil called Cassie is distilled from the flowers[, ]. Traditionally obtained by the 'enfleurage' method, which yields 'cassie pomade', the oil is now more commonly extracted by solvents to yield 'cassie concrete'. The oil is commonly used in perfumery,especially in the preparation of violet bouquets and is extensively used in European perfumery[, ].
Both oils can be processed further into 'cassie absolute'. Cassie absolute processed from concrete is a very expensive oil, only produced in small quantities and employed in high quality perfumery[].
Cassie pomades are manufactured in Uttar Pradesh and the Punjab. A deliciously scented essential oil, it has a fragrance of violets[]. Macerated flowers are placed in melted purified natural fat and allowed to stand for several hours. They are then replaced by fresh flowers and the process repeated until the fat is saturated with perfume. The fat is then melted, strained and cooled. This constitutes the pomade. The odour is that of violets but more intense. Absolute is prepared by mixing pomade or concrete with alcohol (2 - 3 kg to about 4 litres) and allowed to stand for 3 - 4 weeks at about -5°C. The alcohol is then separated and distilled over. The extract obtained is an olive-green liquid with strong odour of cassie flowers[]. The two forms of absolute (from pomade and from concrete) differ in character and are not substiitutes for each other[].
The flowers, or the essential oil obtained from them, are used as an insecticide[, ].

The sweetly scented flowers are placed in the linen cupboard to add a pleasant scent[].

The bark and the fruit are a source of tannin and used in making dyes and inks[, , , ]. The bark and the pods yield a black dye[]. The seedpods contain about 23% tannin[]. The bark, in combination with iron ores and salts, is used as a black dyestuff[].

A gum exuding from the trunk is considered to be superior to gum arabic for use in arts[, ].
A gummy substance obtained from the young pods is used to mend pottery[, ].
A mucilage can be manufactured from the gummy sap[].

The woody branches are used in India as tooth brushes[].

The heartwood is rose-coloured to reddish-brown; the sapwood yellowish. Texture is medium; the grain straight and close. The wood is very heavy, hard, with very good mechanical properties and very durable in the soil. It has an agreeable aroma. When available in sufficient dimensions, it is used for fencing posts, railway sleepers, agricultural implements, furniture, ship building, pegs, woodenware etc[, , , , , , ].
The wood is used for fuel[]. An excellent fuel, widely used in the Americas[].

Propagation

Seed - best sown as soon as it is ripe in a sunny position[]. Stored seed should be scarified, pre-soaked for 12 hours in warm water and then sown. The seed germinates in 3 - 4 weeks at 25°c[]. Plants quickly produce a long taproot and are resentful of disturbance - they should be planted out into their permanent positions as soon as possible[].
Cuttings of half-ripe wood with a heel in a frame[]. Fair percentage[].

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